Johnathan, you were right with the distortion issue at the TX, I am now using these parameters:
./benchma-m dqpsk -f 1.25G -m dqpsk --tx-amplitude=500 -r 1M -M 99999999 --excess-bw=0.35 ./benchmark_rx.py -r 1M -m dqpsk --log --costas-alpha=0.05 -S 4 --verbose -r 1M --gain-mu=0.01 --excess-bw=0.35 -f 1.25G --rx-gain=45 But still, for a 40dB SNR ( http://img149.imageshack.us/img149/4583/screenshot4h.png ) I think we should get a much better constellation than this one ( http://img149.imageshack.us/img149/7968/screenshot3t.png ) I am using the latest gnuradio trunk and the ../gnuradio-examples/digital/benchmark.... I have disabled all the data loggins but the rx_receiver.dat from the /usr/local/lib/python2.5/site-packages/gnuradio/blks2impl/dqpsk.py to reduce the computational requirements. I tried the 0.5M as eric suggested but the results are even worse ( http://img18.imageshack.us/img18/2306/screenshot5hhm.png ) The 2M rate constellation is the same as 1M. If I go with BPSK, I get this: http://img212.imageshack.us/img212/3010/screenshot10.png using ./benchmark_tx.py -m dbpsk -f 1.25G -m dbpsk --tx-amplitude=500 -r 200k -M 99999999 --excess-bw=0.35 ./benchmark_rx.py -m dbpsk --verbose -S 4 -r 200k --excess-bw=0.35 -f 1.25G --rx-gain=30 > debug The image below shows the costas loop error: ( http://img156.imageshack.us/img156/1521/screenshot11.png ) (zoom frequency > http://img514.imageshack.us/img514/2173/screenshot12.png ) blue: phase red: phase_error cian: Q purple: I green: freq So once the costas locks, there is still some error which is causing the blur constellation. But I think that for an almost 40dB SNR signal ( http://img212.imageshack.us/img212/551/screenshot13.png ) we should get much better results. The M&M block influences a lot, if I change the samples per symbol to 2 I get this: ( http://img201.imageshack.us/img201/9436/screenshot14.png ) I have also tried via air interface getting similar results. My question is whether this is normal for the mpsk gnuradio block receiver implementation or I am doing something wrong. What are your thoughts about this? Thank you for your time. -- View this message in context: http://www.nabble.com/QPSK-phase-noise-tp22934944p22950446.html Sent from the GnuRadio mailing list archive at Nabble.com. _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio